Manchester United have invoked options to extend the contracts of Juan Mata, Ander Herrera, Ashley Young and Daley Blind until the end of next season.

The quartet would have become free agents this summer but United have moved to secure the players’ immediate futures and bolster their transfer values by triggering clauses that extend their deals by a further 12 months to June 2019.

United had already triggered the 12-month option in Luke Shaw’s contract before then with the England left back also contracted until at the end of next season. The players are understood to have received letters confirming the extensions.

The longer-term futures of Mata, Blind, Young and Shaw are less clear but by invoking the clauses in the players’ deals United have avoided any immediate complications and given manager Jose Mourinho time to decide what he wants to do with the players.

Marouane Fellaini is out of contract at the end of the season and free to talk to foreign suitors this month, with Besitkas leading the chase for the Belgium midfielder. He has rejected United’s offer of a new contract and, at this stage at least, seems more likely to leave Old Trafford in the summer than extend his five-year stay.

Mourinho does not want to sell Fellaini in the winter transfer window and is prepared to lose him for nothing in the summer if it comes to that rather than recoup a small fee now and be without a player he considers important, despite his current injury problems. Fellaini has made one start since the end of September because of injury.

Blind has been a largely peripheral figure this season and it seems likely that United will listen to offers for the Dutchman. Mata’s future is likely to be influenced by what happens with fellow playmaker Henrikh Mkhitaryan, who is wanted by Inter Milan.

Young has established himself as a first team regular at full back but he will be 33 next July, although with doubts over the future of right back Matteo Darmian, United could seek to keep Young. Shaw has impressed with his attitude and performances in recent weeks and is likely to be given until the end of the season to prove his worth before a decision is made over whether to invest heavily in a new first choice left back.

There are only a finite number of players United could afford to lose in a single summer, especially as Michael Carrick could retire when his contract expires at the end of the season and striker Zlatan Ibrahimovic, also a free agent in the summer, and Fellaini are not certain to stay. Carrick has played just 90 minutes this season following a heart procedure and has been offered a role on Mourinho’s coaching staff.